My understanding is that all revenue flights earn at least 100%, except for those "cash and miles" deals. And if the flight is less than 500 miles, you get the minimum of 500 miles.

The reason for the "at least" is that if you have earned an elite status there are bonuses beyond the 100%.

If you have an account on another Sky Team member like Delta, you can put that number in instead and get the miles credited to that account.

(Note that Continental Flights only give 50% miles when you fly on them and ask for NW miles.)

Romelle